This invention relates to multipole D.C. electric motors with lap-wound coil configurations and, more particularly, to a commutator for a multipole motor having electrically cross-linked commutator bars.
In a conventional multipole D.C. electric motor having a lap-wound coil configuration on the armature, for optimum motor performance, the number of electrical brush pairs (1 positive and 1 negative) is half the number of magnetic poles. Thus, a four magnetic pole motor has two sets of brush pairs or four brushes in total. The brushes are equally spaced around the motor commutator and in the case of the four pole, four brush motor, the brush spacing is an angle of 90xc2x0. The electrical polarity of the sequence of the brushes is positive, negative, positive and negative, which ensures four equally balanced parallel circuits in the armature for optimum motor operation. To apply electrical power to the four brushes, the two positive brushes need to be interconnected and the two negative brushes need to be interconnected. A large brush hold is required with the associated electrical connections between the individual brush pairs since the brushes are spaced at 90xc2x0 from each other.
Recently, it has been proposed to link commutator bars of a wave-wound motor so as to reduce the number of brushes of the motor. However, the winding process is difficult since it is a two-part process requiring indexing and requiring that the commutator links be wound onto the armature with the armature windings. Furthermore, the resulting winding from the wave-wound process consumes much space since there is a great deal of wire between the lamination stack and the commutator.
Accordingly, there is a need to provide an improved commutator for a lap-wound motor by having electrically cross-linked commutator bars connected in a continuous winding process to provide additional parallel paths and thus reduce the number of brushes in a multipole motor.
An object of the present invention is to fulfill the need referred to above. In accordance with the principles of the present invention, this objective is obtained by a method which provides a commutator for a lap-wound motor wherein N is the number of magnetic poles of the motor and N is an even integer greater than 2. The method includes arranging a plurality of commutator bars to be generally equally spaced in a circular arrangement. Sets of commutator bars which are disposed at an angle of 720xc2x0/N therebetween are electrically connected together such that each set of connected commutator bars is electrically isolated from all other sets of connected commutator bars. A lap-winding is then connected to the commutator.
In accordance with another aspect of the invention, a method is provided to connect commutator bars of a commutator for a lap-wound motor, wherein N is the number of magnetic poles of the motor and N is an even integer greater than 2. The method includes arranging a plurality of commutator bars to be generally equally spaced in a circular arrangement to define a commutator. Each commutator bar has a tang extending therefrom. The method further includes:
a) contacting an end of a continuous, conductive member to a tang,
b) moving the member to contact and link a tang which is disposed at an angle of 720xc2x0/N from the previously contacted tang and if N is greater than four, repeating this step until N/2xe2x88x921 links are created,
c) moving the member to contact a tang which is immediately adjacent to the last tang contacted in step b) such that the member defines a bridging portion between the adjacent tangs,
d) repeating step c) until all tangs have been linked by said member, and
e) cutting the bridging portion between said adjacent tangs, thereby electrically connecting certain of said tangs while electrically isolating said certain tangs from other electrically connected tangs.
Other objects, features and characteristics of the present invention, as well as the methods of operation and the functions of the related elements of the structure, the combination of parts and economics of manufacture will become more apparent upon consideration of the following detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification.